The invention relates to a device for the regulation of the charging air pressure for an internal combustion engine provided with an exhaust gas driven turbocharger. The exhaust gas driven turbocharger of the type contemplated includes an exhaust gas driven turbine and a charging air blower. The invention more specifically relates to a regulating device responding to the charging air pressure of the charging air blower for operating a control device arranged in an exhaust canal bypassing the exhaust gas driven turbine.
With internal combustion engines operating with exhaust turbocharging, it is known (DT-OS 1751 061) to limit the charging air pressure to avoid overloading the internal combustion engine and the charging air blower. Thus, charging air is discharged into the atmosphere at a predetermined charging air overpressure by means of a spring-loaded valve arranged in the charging air line whereby a too-high charging air pressure in the charging air line ahead of the output regulating member of the internal combustion engine is avoided at all operating ranges thereof.
In addition, a device is known for the manual regulation of the charging air pressure for internal combustion engines operating with exhaust charging (DT-OS 2 362 133), in which the device for the regulation of the charging air pressure acts together with the charging air pressure in the charging air line of the charging blower and which regulates the quantity of exhaust admitted to the exhaust turbine.
However, with both above-mentioned devices, it is disadvantageous that the temperature of the internal combustion engine is not taken into account.
An object of the invention is to provide a device for the regulation of the charging air pressure for an internal combustion engine provided with an exhaust gas driven turbocharger through which the variable temperature ranges of the internal combustion engine are taken into account.
According to an important feature of the invention, the regulating device for the supply of exhaust gases to the turbocharger is influenced by the temperature of the internal combustion engine, preferably by the temperature of the cylinder head. By this means, it is possible under consideration of the temperature of the internal combustion engine, to adjust the regulating device always to the maximum possible charging air pressure. By this means, it is, on the one hand, assured that the internal combustion engine is not damaged as a result of a too high charging pressure and, on the other hand, that with a cold or moderately warm internal combustion engine, it is capable of a higher output than with a warmer internal combustion engine.
Preferred embodiments of the invention comprise a temperature dependent resistance and a servomotor operatively influencable by this resistance, through which the regulating device is adjustable in the sense of an increase or decrease of the maximum charging air pressure. A difference-amplifier is inserted between the temperature-dependent resistance and the servomotor through which a potentiometer (responsive to the position of a portion of the regulating device), arranged at the regulating device, is influenced.
In other preferred embodiments, an electronic-control follows the temperature-dependent resistance by which electromagnetic valves are controlled effecting an adjustment of the regulating device in the sense of an increase or decrease of the maximum charging air pressure. In contrast to the embodiments with a servomotor, these embodiments are distinguished through an unequally higher switch velocity. The electronic-control comprises an integrated switching circuit through which an equal-current valve is digitalized in a certain number of steps (in the preferred embodiment herein, 16 steps utilizing 16 Opto-couplers and 16 driver-transistors are provided).
These and further objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, several embodiments in accordance with the present invention.